1. Field of the Invention
This invention generally relates to improvements in dental lighting equipment and more particularly to a hanger arm mechanism in the dental lighting equipment designed to enable a lamp head to move around the axis shaftline of the hanger arm.
2. Prior Art
Lighting equipment for use in dental treatment makes it necessary from a functional view point, for the principal axis of the field of lighting to be positioned at right angles with the body axis of a patient by making the field of lighting rectangular in shape; and besides, because a shadowless lamp is used in recent lighting equipment, it is necessary to keep the distance between the lamp head and the oral cavity of the patient substantially definite.
In the prior art, there exists a lighting equipment which is constructed of a horizontally movable arm, a vertically movable arm and a hanger arm. In such equipment, the lamp head is attached to the hanger arm so as to be merely vertically movable; accordingly, operation of an arm mechanism can perform merely dual movement, namely, horizontal and vertical movement to the lamp with respect to a patient so that even if the field of lighting is correnctly positioned with respect to the oral cavity of the patient, when light is cast on the left side or right side interiorly of the mouth of the patient sitting properly with respect to the field of lighting, it is impossible to obtain a satisfactory amount of light unless an object is shifted onto the principal axis of the field of lighting by moving the head of the patient either to the left or to the right side. This inconvenience in handling posed the problem that both the patient and the operator get fatigued by such cumbersome handling.